Ship form



June 4, 1963 N. COSTANZI 3,092,061

SHIP FORM Filed Oct. 19, 1960 7 4 z) j /:f; r-Ti 6 0 Com United States Patent Nicola Costanzi, Trieste, Italy, assignor to Cant en Riuniti Dell Adriatieo S.p.A., Trieste, Italy, a Socneta per Azioni of Italy Filed Oct. 19, 1960, Ser. No. 63,675 Claims priority, application Italy June 30, 1960 2 Claims. (Cl. 114-56) The present invention relates to a ships hull formation at the stern, fitted with a. fin or flow guide intended to decrease the resistance encountered by a ship in her forward motion, such a formation being particularly fit for fast ships propelled by two or more screws.

This invention, in fact, is concerned with the possibility of adapting the shape of the after part of the hull at the load water line and below such a line, so as to reduce as much as possible the water resistance to the forward motion of a ship, leaving unaltered the streamlined form of the after part of the hull above the load water line and generally known as cruiser stern.

It is known that the resistances occurring astern of a ship and which oppose its advancing motion are of two distinct types, and precisely: in the first place the resistances called hydrodynamic of shape which occur below the load water line, and secondly in the case of fast vessels or passenger shipsalso those called aerodynamic of shape which involve all that is above the said water line, always referring only to the after part of the hull.

Up to now for these two resistances occurring astern of ships, namely the underwater resistance and that concerning the poop from the water line upwards, there has not yet been found an univalent solution, and this is the very problem which the present invention intends to solve. As a result of careful trials it was noted that, by retaining the stream-line shape commonly called cruiser stern above the load water line of the hull, and providing such a stern in the area of the flotation level with a fin or flow guide displacing a certain volume and ending aft in an abrupt and blunt way, there is attained the double aim of reducing the aerodynamic resistance of the emergent part of the hull, and at the same time and to a very remarkable extent also the hydrodynamic resistance against the advancing motion of the ship. By means of the above device, there has been obtained a hull whose main feature is to incorporate at its after end, at about the height of its load water line, an appendage of fin-like structure acting as a flow guide, which displaces a certain volume and is intended to expedite and adjust the flow run of the after stream lines and of the propellers jet.

The said fin is attached to the ships after end mainly below the water line, leaving unaltered the upper hull structure emerging from the water and which retains its rounded or streamlined shape (cruiser stern).

In the accompanying drawing:

FIGURE 1 represents the projection, seen from astern, of the hull frame sections with the run of the underwater curves forming the flow guide, and also the curves of the ships after end emerging from the water which do not differ from the conventional cruiser stern.

FIGURE 2 shows, on a different scale for reasons of space, a side projection of the after end of the same ship provided with the said fin or flow guide.

FIGURE 3 shows, on the same scale of FIGURE 2, the plan projection of the longitudinal sections of the after end of the same ship fitted with the underwater fin or flow guide.

In particular: 0, 1, 2, 3 and 4 represent five transversa l section planes with curves having a normal run, while curves 20, 21, 22, 23, and 24 represent the respective deformations made on the same sectional planes by the protruding underwater flow guide or fin. 5, 6, 7, 8, 9 and 10 represent six sectional planes with curves having a normal run, while lines 27 show the deformations made :on sectional plane 7 by the underwater flow guide or fin. 1-1, 12, 13, 14 and 15 represent five vertical sections along as many longitudinal planes of the ship, while lines 31, 32, 33, 34 and 35 show instead the deformations involved on the same sectional planes by the protruding underwater :fin or flow guide. 40 is the lower (underwater) end of the said fin, terminating with a sharp edge; the stern at its lower underwater side ends at its rear end as a plane transverse face or surface as seen in FIG- URE 3 at 40 and this is described on the outside edges by the lines 40, 2t) and the curve 0 of FIGURE 1. The curve 0 is the ordinate between the arcuate aerodynamic cruiser hull extending above the water and the underwater straight transverse plane 40 of FIGURE 2. All three reference characters appear in FIGURE 1. 36 is the ideal line formed by the convergence of the protruding curves 20, 21, 22, 23 and 2 4 with the cross-section frame curves 0, 1, 2, 3, and 4. 37 is an ideal line representing the run of the maximum protrusion of the swell formed by the fin or fiow guide: this line can also be defined as the resultant of the ideal meeting of maximum protrusion of the curves 20, 21, 22, 23 and 24; such a line is mentioned in the present patent application only for the purpose of showing its ascending run towards the stern, this upward run being a specific feature of the flow guide as a whole.

The development of the protrusion and the extent of the said flow guide or fin starts from section curve 0 onwards (towards the stem) and its breadth at section 0 is about 0.25/ 0.35 of the maximum breadth of the vessel. The fins breadth gradually increases in its development towards the stem, as shown by numbers 50, 51, 52, 53 etc., and as a consequence at each successive frame section there is accordingly increased the proportion between the fins breadth and that of the vessel at the respective section, so that at a given frame section (in the present instance section 5) the fin or flow guide has become completely combined within the normal run of the ships body. However it is obvious that the longer is the ship, so much longer will be also the fin with respect to frame section 0, and precisely considering as the fins length the distance from its end at section 0 up to the point ahead where the fin starts protruding from the ships body. Such a length is about one half of the entire length of the ships after end. Lastly, the depth of the fin or flow guide can be determined by the builder for each type of ship, but in genenal the average depth should be about one quarter or one fifth of the fins width at frame section 0. Furthermore, the ideal meeting line 37 between the ascending and the descending surfaces of the fin or flow guide, on both the port and the starboard side of the ship, as already said has an ascending run proceeding towards the stern (compare FIGURE 1), starting ahead below the maximum load water line and terminating astern at frame section 0 slightly above such a line.

The upward inclination toward the stern of the ideal line 37 of maximum protrusion, and respectively of the flow guide or fin as a whole, is determined so as to have, "when the ship is in motion, a run of the said guide parallel to the stream line flow in the area of the flotation level. From the invention of the said flow guide there are obtained the following improvements and technical advancements: from 3 to 6% economization of propelling power at the same speed, in respect to a similar ship not provided with the said flow guide; a better run of the flow or stream produced by the ships propeller; increased stability of hull form and reduced pitching astern.

The aforegoing description and accompanying drawings are to be considered as determinative and not literal expression, and any solution of -the relevant problem arising from the consideration of obtaining a decrease in the resistance encountered by a ship in her motion ahead, by means of a special form of stem fitted at the normal load water line with a flow guide or fin displacing, protruding and having a shape hydrodynamically tangential or parallel to the stream line flow with respect to the normal profile of conventional stern frame sections, is to be attributed to the principle of the present invention.

I claim:

1. A ships hull comprising a flow-guiding rib' formed on both sides of the stern section of the hull symmetrically with respect to the longitudinal centre line of the hull, said rib merging smoothly into the hull at the forward end of the rib and extending rearwardly "with a continuously increasing lateral projection from the hull but lessening overall width and terminating at its rear end in a transverse face, said rib being disposed mainly below.

the mean load water line and being sligthly upwardly inclined both laterally and in the direction towards the stern so as to be parallel to the stream line flow when the ship is in motion.

2. A ships hull comprising a flow-guiding rib formed on both sides of the stern section of the hull symmetrically with respect to the longitudinal centre line of the hull, said rib merging smoothly into the hull at the forward end of the rib and extending rear-wardly with a continuously increasing lateral projection from the hull but lessening overall width and terminating at its rear end in a plane transverse face, said rib being disposed mainly below the mean load water line and being slightly upwardly inclined both laterally and in the direction towards the stern so as to be panallel to the stream line flow when the ship is in motion.

References Cited in the file of this patent UNITED STATES PATENTS 1,313,946 Jenny Aug. 26, 1919 FOREIGN PATENTS 14,633 Norway Oct. 3, 1904 494,791 Germany Mar. 29, 1930 387,986 Great Britain Feb. 16, 1933 

1. A SHIP''S HULL COMPRISING A FLOW-GUIDING RIB FORMED ON BOTH SIDES OF THE STERN SECTION OF THE HULL SYMMETRICALLY WITH RESPECT TO THE LONGITUDINAL CENTRE LINE OF THE HULL, SAID RIB MERGING SMOOTHLY INTO THE HULL AT THE FORWARD END OF THE RIB AND EXTENDING REARWARDLY WITH A CONTINUOUSLY INCREASING LATERAL PROJECTION FROM THE HULL BUT LESSENING OVERALL WIDTH AND TERMINATING AT ITS REAR END IN A TRANSVERSE FACE, SAID RIB BEING DISPOSED MAINLY BELOW THE MEAN LOAD WATER LINE AND BEING SLIGHTLY UPWARDLY INCLINED BOTH LATERALLY AND IN THE DIRECTION TOWARDS THE STERN SO AS TO BE PARALLEL TO THE STREAM LINE FLOW WHEN THE SHIP IS IN MOTION. 